/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Preconditions;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * A future which forwards all its method calls to another future. Subclasses should override one or
 * more methods to modify the behavior of the backing future as desired per the
 * <a href= "http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p>
 * Most subclasses can simply extend {@link SimpleForwardingCheckedFuture}.
 *
 * @param <V> The result type returned by this Future's {@code get} method
 * @param <X> The type of the Exception thrown by the Future's {@code checkedGet} method
 * @author Anthony Zana
 * @since 9.0
 * @deprecated {@link CheckedFuture} cannot properly support the chained operations that are the
 *             primary goal of {@link ListenableFuture}. {@code CheckedFuture} also encourages users
 *             to rethrow exceptions from one thread in another thread, producing misleading stack
 *             traces. Additionally, it has a surprising policy about which exceptions to map and
 *             which to leave untouched. Guava users who want a {@code CheckedFuture} can fork the
 *             classes for their own use, possibly specializing them to the particular exception
 *             type they use. We recommend that most people use {@code ListenableFuture} and perform
 *             any exception wrapping themselves. This class is scheduled for removal from Guava in
 *             February 2018.
 */
@Beta
@Deprecated
@GwtIncompatible
public abstract class ForwardingCheckedFuture<V, X extends Exception> extends ForwardingListenableFuture<V>
        implements CheckedFuture<V, X> {

    @CanIgnoreReturnValue
    @Override
    public V checkedGet() throws X {
        return delegate().checkedGet();
    }

    @CanIgnoreReturnValue
    @Override
    public V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X {
        return delegate().checkedGet(timeout, unit);
    }

    @Override
    protected abstract CheckedFuture<V, X> delegate();

    // TODO(cpovirk): Use Standard Javadoc form for SimpleForwarding*
    /**
     * A simplified version of {@link ForwardingCheckedFuture} where subclasses can pass in an
     * already constructed {@link CheckedFuture} as the delegate.
     *
     * @since 9.0
     * @deprecated {@link CheckedFuture} cannot properly support the chained operations that are the
     *             primary goal of {@link ListenableFuture}. {@code CheckedFuture} also encourages
     *             users to rethrow exceptions from one thread in another thread, producing
     *             misleading stack traces. Additionally, it has a surprising policy about which
     *             exceptions to map and which to leave untouched. Guava users who want a
     *             {@code CheckedFuture} can fork the classes for their own use, possibly
     *             specializing them to the particular exception type they use. We recommend that
     *             most people use {@code ListenableFuture} and perform any exception wrapping
     *             themselves. This class is scheduled for removal from Guava in February 2018.
     */
    @Beta
    @Deprecated
    public abstract static class SimpleForwardingCheckedFuture<V, X extends Exception>
            extends ForwardingCheckedFuture<V, X> {
        private final CheckedFuture<V, X> delegate;

        protected SimpleForwardingCheckedFuture(CheckedFuture<V, X> delegate) {
            this.delegate = Preconditions.checkNotNull(delegate);
        }

        @Override
        protected final CheckedFuture<V, X> delegate() {
            return delegate;
        }
    }
}
